Traditionally, customers made (and still make) telephone calls via the public switched telephone network (PSTN). Modern communications now allow people to make calls over a variety of communications modalities using a variety of devices. These include several packet-switched communications solutions that provide broadband access to the Internet and World Wide Web using, for example, Internet Protocol (IP). Such solutions include digital subscriber line (DSL) service offered by telephone companies (telcos), and data over cable services (e.g., broadband services over the networks traditionally provided by cable television operators, which are often referred to as multiple system operators (MSOs)). Although these packet-based broadband IP networks have been referred to as “fixed” because of the lack of mobility of the on-premises access point, these networks can still include the use of wireless technology. For example, wireless communications can be incorporated in the delivery infrastructure of the fixed packet network (such as satellite or radio transmission towers), and fixed packet networks can employ the use of a wireless access point (such as a wireless router), which can create a local wireless network such as a local Wi-Fi network. Local wireless networks typically have limited range, but provide access to the packet network.
These fixed packet networks have also allowed users to make telephone calls (voice calls) by carrying voice packets over such networks. This technology includes, for example, Voice over IP (VoIP) technology on a broadband IP network.
In other communications technology, mobile/cellular communications devices, such as mobile handsets, have become widely used in modern society. Mobile communications devices such as “smartphones” can allow users to make telephone calls, send or receive electronic mail (e-mail), browse the World Wide Web, check appointments, and get directions, as well as perform many other functions. Such mobile devices typically use cellular networks to handle telephone calls. Cellular networks have also evolved to packet-based communications using Internet Protocol (e.g., 4G LTE service provided by telcos such as Verizon and AT&T).
It is typical for users having cellular phone service to discontinue a phone call on their mobile device and start another call using a fixed communications phone, such as a POTS phone (e.g., telephone connected to the PSTN), or VoIP phone once the users are in their premises. For added convenience, some mobile communication devices include client software that enables the mobile communications device to operate as a multi-modal handset that can communicate via both a non-IP based cellular network, and also via an IP-based packet network, which may be a fixed packet network.
Additionally, a user's multi-modal communication (MMC) device can be configured to allow a user's in-progress communication session, which may be a voice call, to be moved from the mobile/cellular network to the fixed packet (e.g., IP broadband) network, and vice versa, while the user is on the same phone. This “handover” from cellular to IP can occur without any significant notice of interruption or disconnection by the user. For example, a user that initiates a cellular phone call on his or her handset out of the home can continue with the same call on the same handset (but on the IP network) when the user arrives in his/her home. Conversely, if a user having a mobile handset places a call over the IP network, and the signal to the IP network degrades (for example if the user moves outside the premises), the user can continue with the communication on the same mobile handset over the cellular network. Examples of such “fixed-mobile convergence” (FMC) processes are described in U.S. Pat. No. 8,244,251 titled “Concurrent Call Handover,” U.S. patent application Ser. No. 13/631,404 titled “Handover of On-Hold Session between Fixed Packet Network and Cellular Network,” and U.S. Patent Application Publication Number US 2007/0037578 titled “Method and System for Dynamically Modifying A Dial Plan for a Wireless Dual-Mode Handset,” the entirety of each of which is hereby incorporated by reference.
VoIP-based services, whether fixed or mobile, seek to employ a variety of features, which can include call holding (e.g., in the case of a voice call, a logical state in which neither user can hear the other), three way calling/conferencing, voice mail, and call forwarding. Implementations described in this disclosure provide for the establishment of a three-way call via a packet network (which may be an IP fixed packet network or a mobile network) administered by a communications server, including a Session Initiated Protocol (SIP) based server. The SIP protocol is an Application Layer protocol that can operate on Transmission Control Protocol (TCP), User Datagram Protocol (UDP), or Stream Control Transmission Protocol (SCTP). Additionally, SIP is a text-based protocol that incorporates many elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail Transfer Protocol (SMTP).
Like reference numbers and designations in the various drawings indicate like elements.